IMPORTANT MECHANICAL PROPERTIES.

Follwing some importan mechanical properties.

1. Strength: The capacity of material to withstand load is called strength.The strength of material is its ability to sustain loads without rupture or collapse.The maximum stress that any material can withstand is called ultimate strength ortenacity.
2. Elasticity: On a material,when external load is applied it undergoes deformation and on removal of the load if returns to its origanal shape, this property of material is called elasticity.Such a material is called elastic material.
3. Plasticity: If a material does not regain its origanal shape ,on removal of the external load,it is called plastic material.Plasticity is the property of a material by virtue of which material can be moulded in to desire shape. It is the lack of elasticity.
4. Ductility: If a material undergo a considerable deformation ,without rupture it is called a ductile material and this property of material  is called ductility.Most ductile material is steel and grey castiron is least ductile material.As temperature increases,ductility increases.
5. Brittleness:If material can notundrgo any deformation,when some external forces act on it and it fails by rupture,it is called a brittle material.Brittle materials are stronger in compression and weak in tension.Materials having less than 5% elongation are considered as brittle.
6. Malleability:It is property of a material by virtue of which material can be converted in to thin sheets by hammering.Malleable material can be easily rolled and forged without cracking or breaking.Gold is the most malleable material while cast iron is the least malleable material.This is also a compressive quality of a material.
7. Toughness:Capacity of a material to absorb energy before rupture is called toughness.
8. Hardness:Resistance of a material to abrasion,wear and scratches is called hardness.An alloyed cast iron is the hardest material while magnesium alloy is the softest material.
9. Stiffness:Resistance to deformation or strain is called stiffness.Force required to produce unit deformation in a material is called stiffness.Steel is considered as a stiffer material.
10. Endurance: The capacity of a material to withstand repeated stress cycles is known as Endurance of a material.
11. Fatigue strength:The maximum sress,which a material can withstand,under repeated stress cycles without fracture is called "fatigue strength".
12. Endurance limit:For most of materials there is limiting stress below which a stress or a load may be repeated infinite number of times without causing failure.This limiting stress is known as endurance limit or fatigue limit.
13. Homogeneous material:Homogeneous material means that the material of the member is of the same kind throught  its length.For example,if a beam is made of steel,the material of beam does not change throught the length of the beam.
14. Isotropic material:Isotropic means it possesses the same elastic properties in all the directions.

SPUR GEAR TERMINOLOGY.

The important definitions related to spur gear are as follows:

PITCH CIRCLE:  it is an imaginary circle on gear, by which pure rolling action would transfer the same motion and power as the actual gear. It is the basis of measurement for other parameters of gear.

ADDENDUM CIRCLE: it is the circle drawn through the top of the teeth which is concentric to the pitch circle.

DEDENDUM CIRCLE: it is the circle drawn through the bottom of the teeth. It is also called as root circle.

PITCH CIRCLE DIAMETER (D): it is the diameter of pitch circle. The size of the gear is usually specified by the pitch circle diameter.

MODULE (m): it is the ratio of the pitch circle diameter to the number o f teeth on gear.

CIRCULAR PITCH (Pc): it is the circular distance measured along the circumference of pitch circle from a point of one tooth to the corresponding point on adjacent tooth.

DIAMETER PITCH (Pd):It is the ratio of number of teeth to the pitch circle diameter.

ADDENDUM: it is the radial distance of tooth from the pitch circle to the top of the tooth. Its standard value is one module.

DEDENDUM: it is the radial distance of tooth from the pitch circle to the bottom of the tooth. Its standard value is 1.15.

CLEARANCE : it is the radial distance between the top of the tooth of one gear to bottom of the tooth of another mating gear. Its standard value is 0.157.

TOTAL DEPTH: it is the radial distance between the top of the tooth to bottom of the tooth. it is equal to the sum of the addendum and dedendum of a gear.

WORKING DEPTH: it is the radial distance from addendum circle to the clearance circle. It is equal to the addendum of two mating gears.

TOOTH THICKNESS: it is the width of the teeth measured along pitch circle.

TOOTH  SPACE: it is the space between two adjacent tooth measured along the pitch circle.

BACKLASH: it is the distance between tooth space and tooth thickness measured along the pitch circle.

FACE OF TOOTH: it is the surface of the gear above pitch circle.

FLANK OF TOOTH: it is the surface of the gear below pitch circle.

TOP LAND: it is the surface at the top of the tooth.

#2.SPUR GEAR TERMINOLOGY |IN HINDI| |KOM|. https://youtu.be/LE4P14mqyGw

what is interference in involute gear?

This thing only happen in case of involute gear.For constant valocity ratio the profile of both mating gear should be tangent all time.As we know that below the base circle it is not involute profile of teeth,so when tip of other teeth come in contact with the surface of other mating teeth below the base circle,there will happen undercut of teeth below base circle,it is called interference of gear.To avoid this normally undercut is already provided below the base circle of gear.

      In brief,the phenomenon when the tip of a tooth  undercuts the root on its mating gear is known as interference.

what is preferred series?

preferred series are the series of numbers obtained by geometric progression and rounded off.

what is basic preferred series?

There are five basic preferred series designated as R5,R10,R20,R40 and R80. Their step ratios are 1.58,1.26,1.12,1.06 and 1.03 respectively.

       Each series is established by talking the first number one and multiplying it by a step ratio to get second number. The second number is then multiplied by a step ratio to get third number. The procedure is continued until the complete series is built up.

ADVANTAGES OF PREFERRED SERIES:

1. The difference in two successive terms has fixed percentage.
2. Provide small step for small quantities and large steps for large quantities. It is in conformation with mode of vibration found in nature.
3. The product range is covered with minimum number of sizes without restricting the choise of the customers.